March 21st: 3 facts you need to know about Down Syndrome (on World Down Syndrome Day)

1. Down Syndrome is a common condition.

Down syndrome occurs at the rate of around 1 in 1000 live births in the UK.

Down syndrome is the most common cause of significant intellectual impairment. Based on published research and general population figures, there are currently around:

30,000 people with Down syndrome in the United Kingdom.

200,000 people with Down syndrome in Western Europe.

more than 2,000,000 people with Down syndrome worldwide.

2. Down syndrome is the result of a genetic variation.

Each cell in the body usually has 23 pairs of chromosomes (46 in total). Individuals with Down syndrome have an additional copy of chromosome 21 in all or some of the cells in their body (making 47 chromosomes in total).

There are three main types of genetic variation that cause Down syndrome:

Trisomy 21 – all of the cells in the body have an extra copy of chromosome 21 (this is why Down Syndrome Day is on the 21st). This is the most common type of Down syndrome, found in at least 9 out of 10 people with the condition.

Translocation – all of the cells in the body have additional chromosome 21 genetic material attached to another chromosome. Only around 1 in 20 people with Down syndrome have the translocation form of the condition.

Mosaic – only some of the cells in the body have extra chromosome 21 genetic material. Only around 1 in 50 individuals with Down syndrome have the mosaic form of the condition.

3. Down syndrome can affect any family

The reason for the presence of additional chromosome 21 genetic material at the time of conception is still unknown.

Although the risk of having a baby with Down syndrome increases with maternal age, babies with Down syndrome into families from all social, economic and racial backgrounds, and to parents of all ages.